Thank you for the additional information,

Can you try switching to DirectX 9 mode and see if there is any difference, this can be done on the launcher under 'Config.' Simply turn off DirectX 11 mode. Additionally, try lowering some graphics settings or resolution (even if your PC can obviously handle it).

If those don't work, try temporarily disabling your anti-virus/firewall and see if the problem persists. I'd also try turning off any overlay program (such as the Geforce Experience you mentioned) as this may be potentially interfering with the game.

If all else fails, you may want to try reinstalling the whole game. Make sure to delete any remaining FFXIV files from your computer, including any potential files in your ‘Documents’ folder. Then reinstall the game from scratch. If you need a digital version of this, it can be found here: http://www.finalfantasyxiv.com/playersdownload/na/. Any updates or expansions will be downloaded to your computer once logged into the appropriate account.

Please let us know if one of these suggestions solves your issue so we may better assist others who run into the same problem.